Heretofore, resin for use in electrical and electric parts is imparted with flame retardancy by a flame retardant according to the intended use and the portion for which the resin is used. As the flame retardant, bromine flame retardants, phosphorus flame retardants, inorganic flame retardants, silicone flame retardants, and the like are known. For example, the phosphorus flame retardant is kneaded with resin containing aromatic polyester and a styrene polymer (PC+ABS or PC+AS) which has been frequently used for copying machines, and the resin is imparted with the flame retardancy of V-2 to 5VB of the UL94 standard relating to the flame retardancy of resin materials according to the intended use.
On the other hand, a biomass-derived resin containing plants as the raw materials has drawn attention from the viewpoint of a reduction in petroleum resources. For example, polylactic acid containing starch, such as corn, as the raw materials is mentioned. With respect to the biomass-derived resin, the strength and the flame retardancy are improved by an alloy with a petroleum-derived resin and an additive, and then the biomass-derived resin is practically used for cases of copying machines and the like.
However, the flame retardants contain resources of concern for exhaustion, such as petroleum resources and minerals. Thus, the development of a flame retardant utilizing renewable resources, such as plants, has been demanded from the viewpoint of environmental protection.
Among the flame retardants which impart flame retardancy to resin, as substances synthesized using plants as the raw materials, tannin described in PTL 1 (Japanese Patent No. 4382617), potassium hydrogen tartrate described in PTL 2 (Japanese Patent Laid-Open No. 2002-348575), and a phosphorus containing polymer composite salt containing phytic acid described in PTL 3 (Japanese Patent Laid-Open No. 2009-1747) are known.
As the flame retardants obtained from plants, tannin, potassium hydrogen tartrate, and a phosphorus containing polymer composite salt containing phytic acid are known. When these substances were added to aromatic polyester and a styrene polymer (PC+ABS), an impact resistance as high as 5 kJ/m2 or more in terms of Charpy impact strength was obtained.
However, the fire retardancy of 5VB of the UL94 standard required when used for cases of copying machines were not developed. This is considered to be because the tannin, the potassium hydrogen tartrate, and the phytic acid are hydrophilic, and therefore they have low compatibility with resin.